Quaking Aspen Black Branches: Sooty Mold from Scale Insects

Tree Has Black Leak Fungus, Flat Black Branches, White Trunk

Planted March in NH. Treated with mycorrhizal fertilizer. Asks if it kills fungus or controls. Branches black, trunk white.

Expert Diagnosis

Likely sooty mold from insect excrement (aphids, scale). Rubs off wet. Control insects, not fungus. Mycorrhizae boost root health. Rake/burn fallen leaves in winter to reduce leaf-spot fungi. For tall trees, spraying impractical; raking is cost-effective.

Follow-Up

Owner confirms black rubs off, finds scale insects burrowed in wood. Expert: rake/burn leaves pre-spring, apply Bayer soil drench (imidacloprid) per label. Scale bodies persist after death; monitor population.